Overload-circuit breaker for motors started by means of a starting resistance



May 26, 1925. 1,539,429

w. SARTIG OVERLOAD CIRCUIT BREAKER FOR MOTORS STARTED BY MEANS OF ASTARTING RESISTANCE Filed March 10, 1922 til Patented May 26, 1925.

UNITED STATES PATENT OFFICE.

WILLY SARTIG, OF ESSEN, GERMANY, ASSIGNOR 'IO FRIED. KRUIP AKTIENGESELL-SGHAFT, 0F ESSEN-ON-THE-RUHR, GER-MANY.

OVERLOAD-CIRCUIT BREAKER FOR MOTORS STAR-TED BY MEANS OF A STARTINGRESISTANCE.

Application filed March 10, 192-2.

To all ill/1077b it may concern:

Be it known that I, VILLY San'ric, residing at Essen, Germany, a citizenof the German Republic, have invented a certain new and usefulImprovement in Overloadlircuit Breakers for Motors Started by Means of aStarting Resistance, of which the following is a specification.

This invention relates to improvements in overload circuit-breakerswhich are designed to protect electric motors from overload and thesensibility of which varies automatically during the starting of themotor to be protected, such as disclosed for example in the applicationfor Letters-Patent of the United States filed December 29, 1921, SerialN o. 525,695 in the name of Felix Tobien.

The present invention has for its object to provide an overloadcircuit-breaker of this character the sensibility of which is increasedas. long as a body which is moved on a prescribed track by the electricmotor to be protected, is within a definite section of this track.

The invention is especially adapted for use on electrically drivenvehicles or cranes which should travel at reduced speed on one or moresections of their track.

lVith the aforesaid end in view the invention consists in thearrangement, construction and combination of parts to be hereindescribed and particularly pointed out in the appended claims.

The drawing shows, by way of example, av diagram according to theinvention in which the motor to be protected is designed to drive atravelling crane.

Referring now to the drawing, A designates the current feeding line andB the trolley. Connected in series with the trolley B are: the maincurrent releasing coil C, the break of the overload circuit-breakerwhich consists of two stationary contact-points C and C and a movablecontact member C actuated by the releasing coil C and adapt ed to bridgethe two contact-points, the starting resistance D along with its slidingcontact 41 and the main current motor E E, the field winding E of whichis grounded by one of its ends. A current branch including a magnet coilC and a series resistance C is connected in parallel to the releasingcoil C and the break C C The magnet coil 0 acts in the same sense asSerial No. 542,736.

the releasing coil 0 and it works on the same magnetic circuit as thereleasing coil C. The exciting force of the magnet coil 0* is determinedin such a manner as to be unable to open the overload circuit-breakerwhen same in closed position, while it is adapted to hold thecircuit-breaker, when opened, in its cut-out position contrary to theaction of a tension spring C which engages the movable contact member CConnected in. parallel with the main current motor E E is a line K whichcontains another magnet coil G for the overload circuitbreaker and aseries resistance G. The magnet coil C likewise acts on the samemagnetic circuit and is wound in the same sense as the magnet coils Cand C The circuit K further comprises a contact device consisting of aconductor bar M and a sliding contact M The sliding contact M isattached to the frame N of the crane, whil the conductor bar M isarranged parallelly to the track P of the crane-frame N and is of suchlength as to cause the sliding contact M and the current bar M to remainin contact along the whole section of the track P on which the craneshould travel at reduced speed.

In the position of the several parts, shown on the drawing, in which thesliding contact M is in contact with the conductor bar M, in, which thestarting resistance D is partly switched oil and. in which the overloadcircuitbreakcr is closed, the magnet coils (l and C are energized sothat the overload circuit-ln'eaker possesses comparatively highsensibility. The degree of this sensibility conforms to the strength ofthe excis tat-ion of the magnet coil 0". This excitation as well as thespeed at which the crane is driven, depend u pen the size of theswitchedin portion Oil: the starting resistance D. a

If the speed of the crane is increased by switching oil further steps olthe starting resistance, the sensibility of the overload circuit-breakerwill. likewise be increased for the reason stated above. Now the size ofthe series resistance G is such as to cause the sensibility of theoverload circuitbrealrer to become so high, at a definite speed of thecrane which is lower than the speed attainable with entirely cut-outstart ing resistance, that the circuit-breaker will enter into action,provided, of course, that the contact device M M is still closed.

As soon as the sliding contact M leaves the conductor bar M in thefurther course of the travelling motion of the crane, the magnet coil CWill be de-energized and the sensibility oi the overload circuit-breakervill be accordingly reduced, so that the crane can be driven at a higherspeed on the track-sections situated beyond the section limited by thecurrent bar v1.

It will be obvious that it Will be Within the scope of the presentinvention to provide still other conductor bars to be connected inparallel with the conductor bar M and arranged at other places of thecrane-track P, such as for example at the ends of the track. Further,the circuit K which includes the magnet coil can be connected to includethe armature E alone instead of the motor E E.

Claims:

1. In combination with an electric motor, a body propelled by saidmotor, a prescribed track for said body, a main circuit in connectionwith said motor, an overload circuit breaker having a main currentreleasing coil in said circuit, an auxiliary coil for supplementing theaction of said main current releasing coil, and means for automaticallyexciting said auxiliary coil at predetermined points in the travel ofsaid body.

2. In combination with an electric motor,

a body propelled by said motor, a prescribed track for said body, a maincircuit in con- I nection with said motor, an overload circuit breakerhaving a. main current releasing coil, a shunt circuitin connection withsaid main circuit, an auxiliary coil for supple menting the action ofsaid main circuit current releasing coil disposed in said shunt circuit,and means for automatically opening or closing said shunt circuit atpro-dotermined points in the travel of said body.

3. In combination with an electric motor, a body propelled by saidmotor, a prescribed track for said body, a. main circuit in connectionwith said motor, an overload circuit breaker having amain currentreleasing coil, a shunt circuit in connection with said main circuit, anauxiliary coil for supplemcnting the action of said main circuit currentre easir coil disposed in said shunt circuit and means for automaticallyopening or closing; said shunt circuit at predetermined points in thetravel of said body, said means comprising a contact device disposed insaid shunt circuit. one of the members of said cont-act device beingarranged along said track and the other member of said contact devicebeing attached to said body.

The foregoing specification signed at Rssen, Germany, this 26th day ofJanuary,

WILLY SARTIG.

